Due to the exhaustion of traditional energy sources together with an increase in the global energy demand, impetus is currently being given to the development of alternative energy sources. Among them, biomass is renewable quantitative biological resource that attracts a great deal of attention.
Among biomass-based industrial raw materials, isosorbide (C6H10O4) that is prepared by dehydration of sorbitol (C6H14O6) attracts attention as an environmentally friendly raw material for preparing polycarbonate (PC) as a substitute for bisphenol A (BPA), an epoxy monomer or an environmentally friendly plasticizer. Namely, isosorbide, a material that can be obtained by simple dehydration of sorbitol, is attracting attention as a monomer required for synthesis of next-generation, high-performance, environmentally friendly materials that can replace conventional polymer products, and many studies thereon have been conducted.
Environmentally friendly materials generally show poor properties compared to petrochemical-based materials, whereas isosorbide advantages in that it is environmentally friendly and, at the same time, shows excellent properties compared to conventional petrochemical-based materials. In addition, isosorbide may be used as an additive that can make plastic materials stronger and tougher, and that is also used as an agent for treating cardiac diseases by being boded to nitrate.
When D-glucose obtained from biomass by pretreatment is hydrogenated in the presence of a catalyst, sorbitol is produced. Isosorbide is produced by double dehydration of sorbitol. This cyclization reaction is influenced by various reaction conditions, including temperature, pressure, solvent, catalyst, etc.
Currently, as a method of producing anhydrosugar alcohols, including isosorbide, a process is widely used in which sulfuric acid is used as a catalyst and a reaction is carried out under reduced pressure (Korean Patent No. 10-1079518). However, when a strong acid catalyst such as sulfuric acid is used, a reactor is easily corroded, and for this reason, an expensive reactor should be used in order to prevent the corrosion of the reactor. Furthermore, a large amount of energy is continuously consumed to maintain a vacuum level, and thus the production cost is increased. In addition, because it is not easy to manufacture a continuous vacuum reaction system with high reliability, most processes are carried out using a batch type or semi-batch type reactor.
Meanwhile, anhydrosugar alcohol has a high boiling point and is easily decomposed by high-temperature heat and thus anhydrosugar alcohol is difficult to separate by general atmospheric pressure distillation. For this reason, a vacuum distillation process is frequently used (U.S. Pat. No. 6,639,067). However, there is a disadvantage in that the production cost increases rapidly, because a vacuum level should be maintained not only in the reaction process, but also in the separation process, and because the yield of anhydrosugar alcohol decreases when a multi-step process is carried out.
Accordingly, the present inventors have conducted studies to solve the above-described problems, and as a result, have found that, if an anhydrosugar alcohol is produced by heating a reactor while supplying a mixture of a catalyst and a sugar alcohol to the reactor, and, at the same time, the anhydrosugar alcohol is separated by distillation, after which melt crystallization is performed, a high-purity anhydrosugar alcohol can be produced in high yield by a simple process, thereby completing the present invention.